1. Technical Field
The present disclosure relates to an electrostatic chuck having an elastomer layer and a method of manufacturing the same.
2. Background Art
In recent years, a size of the flat panel display (FPD) typified by the liquid crystal display device is increased, and the method and structure for stably-supporting a large-sized glass substrate becomes more and more important in the manufacturing steps of the FPD.
For example, the liquid crystal display device is manufactured in such a manner that two sheets of glass substrates on which color filters, a thin-film transistor array, etc. are provided are bonded together using a sealing material at an interval of about several microns, and then the liquid crystal is filled in the interval and sealed in the two sheets of glass substrates.
A method of filling and sealing the liquid crystal are carried out under vacuum. More particularly, the sealing member is coated on either of two glass substrates to be pasted and also the liquid crystal is dropped onto either of two glass substrates, and then two sheets of glass substrates are bonded together while applying a pressure, thereby sealing the liquid crystal.
In such manufacturing steps of the FPD, the chucking method based on a static electricity (the electrostatic chuck) has been used as the method of supporting the glass substrates under vacuum (at a low pressure).
For example, as a structure of the electrostatic chuck, such a structure has been proposed in which an insulating film is bonded to a substrate (base) made of metal material and also electrodes are provided to the substrate (see JP-A-2004-235563, for example).
However, when the large-sized glass substrate is chucked by the electrostatic chuck, in some cases, a warpage occurs in the substrate due to its own weight of the substrate. As a result, sometimes it is difficult to chuck the substrate using the electrostatic chuck with good precision.
For this reason, an elastomer layer for absorbing a stress caused by a deformation of the substrate is provided between a chucking portion including the electrode to which a voltage is applied, and the metal base on which the chucking portion is provided. At this time, an uneven pressing force caused by the warpage of the substrate can be absorbed by the elastomer layer, and thus it is possible to chuck the large-sized glass substrate with good precision.
However, when the elastomer layer is bonded to the metal base, in some cases, an air enters between the elastomer layer and the metal base, and a bubble is thus formed. In cases where such a bubble is formed and the electrostatic chuck is used at a low pressure, for example, the chucking surface bulges partially and thus a chucking force of the glass substrate is weakened and breakage of the glass substrate is brought about, and others. As a result, in some cases there is a problem that reliability of the electrostatic chuck is decreased.